The present invention relates to an image projecting device and an image projecting method for displaying an image by projecting light corresponding to image information onto a screen or the like.
Recently, image projecting devices for projecting image information such as a video signal or the like onto a screen, or so-called projectors have been increasing in screen size. Less expensive products have been developed and going into not only office use but also household use. These devices have a plurality of high-luminance lamps or lasers incorporated therein for a larger screen and viewing even in a bright room.
With a device using a laser, laser light can enter the eye of a person and affect the eye. Thus, in order to ensure laser safety, international standards IEC-60825 precisely specify how to use devices using a laser according to laser output.
As for projectors that scan a laser and project the laser onto a screen, laser show guidance in the international standards IEC-60825-3 defines 3 m or more in an upward direction from a floor and 2.5 m or more in a horizontal direction in an area that an audience can enter.
In practice, however, there are not so many theaters that can project a laser at such a sufficient distance from an audience, and projection in other than theaters will be limited.
In order to conform to the specifications of the guidance in the international standards IEC-60825-3, Automatic Power Reduction (APR) is proposed as a method for preventing exposure of an audience to a laser. For example, a safety device of a projection type television receiver is proposed. The safety device of the television receiver includes detecting means for detecting entrance of a moving object into a projecting area from a projecting optical system to a screen. Output of a light source is controlled on the basis of a detection output from the detecting means to reduce or interrupt the light output (see Patent Document 1, for example).
Such a safety mechanism uses an infrared sensor as the detecting means. When simply using the sensor, it is not possible to detect a person moving at a long distance from a position of the sensor. Thus, this method lacks in suitability for embodiment as a method capable of detection.
For example, even for a sensor capable of detection at a short distance of about 5 m, detection at a long distance of 10 m or more is not easy.
[Patent Document 1]
Japanese Patent Laid-open No. Hei 4-111585